Study On Micro Removal Mechanism Of Chemical Mechanical Polishing Of SiC

Silicon carbide(SiC)is a representative third generation semiconductor material,which plays an important role in the modern electronic information industry.However,SiC has many characteristics such as high hardness,high brittleness and chemical inertia,which makes it difficult to process SiC and high cost,which hinders the wider application of SiC.Chemical mechanical polishing(CMP)is the only way to realize the global polishing of SiC surface.At present,the research on the CMP technology of SiC only exists in the experimental stage,and lacks the deep research on the removal mechanism and chemical reaction process during the friction removal process.In this paper,the molecular dynamics simulation method of Reax FF reaction force field is used to simulate the SiC chemical machine The mechanical polishing mechanism of SiC chemical was studied and explored from the micro point of view.Molecular simulation method is an effective method to study the micro system,because the classical molecular dynamics simulation method can not simulate chemical reactions,quantum mechanics calculation can only be applied to the simulation of small systems,so this paper uses a new simulation method of Reax FF based on the bond level change.This method can simulate both large system and chemical reaction,and is suitable for the study of removal mechanism of SiC CMP.The simulation of Reax FF needs the parameters of corresponding simulation system.In this study,the SiC chemical mechanical polishing simulation system includes Si,C,H,O and other elements.Due to the lack of parameter set suitable for the simulation system,in this paper,the annealing algorithm is used to fit the parameters needed in this simulation.The state energy,charge and surface binding energy of the fitting parameters are compared by DFT calculation method,which is in good accordance with our simulation requirements.Based on molecular dynamics simulation of Reax FF reaction force field,a chemical mechanical polishing model of Particles-Solution-SiC was designed.The reaction products of Si and C atoms on SiC surface in hydrogen peroxide solution were explored,and the removal process of Si and C atoms in chemical mechanical polishing was traced.The results showed that the Si atoms on silicon carbide surface would produce a large number of Si-OH bonds in hydrogen peroxide solution.During the friction process,Si-O will be formed with Si atoms in Si O2 abrasive particles The Si-O has high bond energy and is not easy to break.During the process of bonding,Si atoms on SiC surface are removed.C atom in SiC is not easy to be oxidized.When the Si atoms around C atom are removed,the position structure of C atom will be changed,and C atom loses its original stability and is finally removed.In this paper,the effect of Si-OH on polishing is verified by using the-OH terminal of all Si atoms on the surface of SiC.In addition,the pure water is used as polishing liquid as the comparative study.It is found that the oxidation of H₂O₂will improve the efficiency of chemical mechanical polishing of silicon carbide,and the removal rate is positively related to pressure.Temperature is also an important factor affecting the chemical mechanical polishing of SiC.The polishing temperature is 300K,1000K,2000K,and the pressure is 1GPa.The results show that there is a significant difference in the polishing effect of SiC at different temperatures.at 300K temperature,due to the low pressure,almost no atoms are removed;when the temperature rises to 1000K,34 atoms of silicon carbide are removed after polishing 500ps,which is much higher than the number of atoms removed at 4GPa pressure at 300K temperature;when polishing at 2000K,a large number of atoms on the surface of SiC are removed,the number is multiple it accounts for one tenth of the total number of SiC substrates.Therefore,it is speculated that high temperature will change the chemical properties of SiC.This paper designed the simulation experiment of SiC and water at high temperature to study the influence of high temperature on the chemical reaction ability of silicon carbide.The results show that the reaction phenomena of SiC and H₂O at different temperatures are very different.At 300K,the reaction on the surface of SiC is chemical reaction to the unsaturated atoms on the surface of silicon carbide.When the temperature reaches 1000K,the atoms on the surface of SiC begin to be oxidized and Si-O-C bond is formed.At 2000K,the oxidation reaction on the surface of silicon carbide increases obviously,O atoms begin to invade into SiC,and at 3000K,the reaction is stable Chemically inert silicon carbide can react violently with water.SiC is deeply eroded and the whole structure is seriously damaged.In addition,with the increase of temperature.The erosion depth of H and O atom on SiC substrate increases,which indicates that the increase of temperature will obviously change the chemical properties of SiC.